I am trying to find what the spec is for the measurement between the front and rear takedown pins on an AR lower is.
Also, I am trying to find what is considered to be “within spec” for the width of the ears on the upper receiver that mate with the pins in the lower receiver…
(No, I haven’t been drinking, I just don’t know what the technical term is for the parts in question…)
I did a search for this information, but I couldn’t find anything in the way of exact dimensions.
www.biggerhammer.net/ar15/cad/ar15_receiver.pdf
This should also help.
The “ears” in question are called lugs.
http://www.cncguns.com/projects/ar15lower80tutorial-1.html
Edit: Kwelz beat me to it!
Thanks for the links.
Looks like the correct dimension is .491 on the lower, now if I can just find the measurement for the lugs on the upper receiver…
center to center on the 0.251" +/- 0.001" holes is 6.375" +/- 0.002"
My Colt/ FN print for the lower shows 0.500" + 0.004" where that BiggerHammer print shows 0.500" - 0.004" at the pivot pin lug recess, looks like an error on the BH print as the half width dim next to that one shows 0.252" allowable. It also shows 0.500" + 0.005" at the takedown pin lug recess.
the 0.491" isn’t related to the takedown pin lug, that’s the boss for the auto sear.
Thanks…
I guess that my ability to read blueprints is lacking…
don’t feel like the Lone Ranger, that BH print hurts my head to look at. I just pull out paper.